Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 250005 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 805 PM EDT THU APR 24 2014 .SYNOPSIS... HIGH PRESSURE SLIDES OFFSHORE TONIGHT. LOW PRESSURE TRACKS FROM THE OHIO VALLEY ACROSS THE NORTHERN MID ATLANTIC FRIDAY...AND OFF THE COAST FRIDAY NIGHT. A COLD FRONT DROPS ACROSS THE REGION SATURDAY NIGHT...WITH HIGH PRESSURE BUILDING IN FROM THE GREAT LAKES SUNDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... CURRENT WV IMAGERY INDICATES AN UPPER TROUGH STEADILY TRACKING W-E ACROSS THE CENTRAL PLAINS...WITH ANOTHER TROUGH DOWNSTREAM OF THE LOCAL AREA OVER ATLANTIC CANADA. A NARROW RIDGE AXIS EXISTS OVER THE SOUTHEAST AND OHIO VALLEY...WITH SURFACE HIGH PRESSURE UNDERNEATH THIS FEATURE EXTENDING FROM THE EASTERN GREAT LAKES THROUGH THE MID ATLANTIC. THE CENTRAL PLAINS TROUGH WILL LIFT NE THROUGH THE MID MISSISSIPPI VALLEY TOWARD THE GREAT LAKES OVERNIGHT. MEANWHILE...SURFACE HIGH PRESSURE WILL SLIDE OFFSHORE. THE SKY SHOULD BE MAINLY CLEAR THROUGH THE EVENING AND EARLY OVERNIGHT HOURS...BEFORE CLOUDS BEGIN TO INCREASE OVER WESTERN PORTIONS LATE. THE TEMPERATURE SHOULD DROP QUICKLY THROUGH THE EVENING HOURS...WITH COOL DRY HIGH PRESSURE OVER THE AREA...AND BECOME STEADY AFTER MIDNIGHT. LOWS SHOULD RANGE FROM THE UPPER 30S TO LOW 40S OVER INTERIOR PORTIONS E OF I-95...WITH LOW/MID 40S W DUE TO INCREASED MIXING (FROM LIGHT SE FLOW) AS THE HIGH SHIFTS OFFSHORE AND THE APPROACH OF LOW PRESSURE FROM THE W. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... THE PARENT TROUGH LIFTS THROUGH THE GREAT LAKES FRIDAY...WITH SURFACE LOW PRESSURE TRACKING ACROSS THE NORTHERN MID-ATLANTIC. A PROMINENT (SURFACE AND MID-LEVEL) THETA-E RIDGE PRECEDES THE TROUGH AXIS. THIS SHOULD PRODUCE AN INCREASE IN BOUNDARY LAYER MOISTURE THROUGH THE MORNING. FORECAST SOUNDINGS SHOW A PERIOD OF RATHER DEEP MOISTURE ALONG WITH A PERIOD OF MODEST LIFT PASSING ACROSS THE LOCAL AREA LARGELY IN THE 18-00Z TIMEFRAME. GIVEN THIS THERE IS HIGH CONFIDENCE OF SHRA AND EMBEDDED TSRA PASSING ACROSS THE AREA. THE BEST DESTABILIZATION OCCURS OVER SE PORTIONS. THIS WILL BE IN THE PRESENCE OF MODEST DEEP LAYER SHEAR (~35KT 0-6KM)...AND ~30KT OF 0-1KM BULK SHEAR. AT THIS TIME INSTABILITY APPEARS TOO MARGINAL TO SUPPORT ORGANIZED SEVERE WEATHER...BUT THERE IS ENOUGH SHEAR FOR A MINIMAL THREAT MAINLY ACROSS FAR SE VA/NE NE. HIGHS SHOULD GENERALLY BE IN THE LOW/MID 70S (LOCALLY COOLER ALONG THE COASTS). THE MID-LEVEL COLD FRONT (COLD THETA-E BOUNDARY) MOVES OFF THE COAST LATE FRIDAY NIGHT...WITH DRIER AIR ARRIVING FROM THE W. THE SURFACE BOUNDARY IS MAINLY A WIND SHIFT...SO TEMPERATURES SATURDAY SHOULD GENERALLY BE A FEW DEGREES WARMER THAN FRIDAY. HIGHS ARE EXPECTED TO RANGE FROM THE MID 70S OVER EASTERN PORTIONS (LOCALLY COOLER ALONG THE IMMEDIATE COAST)...TO AROUND 80 ALONG A W OF I-95. THIS WILL BE AFTER MORNING LOWS RANGING FROM THE UPPER 40S NW...TO UPPER 50S SE. SATURDAY SHOULD BEGIN MOSTLY SUNNY...BEFORE CLOUDS INCREASE (ESPECIALLY N) AHEAD OF A COLD FRONT APPROACHING FROM THE NW. AT THIS TIME POPS WILL BE HELD BELOW 15%...BUT A FEW SPRINKLES ARE POSSIBLE ACROSS THE FAR NORTHERN PORTIONS. THIS FOLLOWS MORE OF A 12Z GFS/ECMWF SOLUTION RATHER THAN THE MORE MOIST 12Z NAM DUE TO THE EXPECTATION OF LIMITED BOUNDARY LAYER MOISTURE. THE COLD FRONT DROPS THROUGH THE AREA SATURDAY NIGHT...WITH HIGH PRESSURE BUILDING IN FROM THE GREAT LAKES SUNDAY. LOWS SHOULD RANGE FROM THE MID 40S TO LOW 50S SUNDAY MORNING...FOLLOWED BY HIGHS SUNDAY AFTERNOON IN THE MID 60S NE TO LOW/MID 70S SW UNDER A MOSTLY SUNNY/CLEAR SKY. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A HIGHLY AMPLIFIED/BLOCKY PATTERN WILL RESULT IN AN UNSETTLED PRD NEXT WEEK. TODAYS MODELS CONTINUE TO SLOW THE ARRIVAL OF PCPN UNTIL MON AFTRN WHEN THE STALLED FRONTAL BNDRY ACROSS THE CAROLINAS BEGINS TO MOVE BACK NORTH AS A WARM FRONT. KEPT SUNDAY NIGHT AND MON MORN DRY AS HIGH PRS TO THE NORTH IS SLOW TO RETREAT. LOWS M40S-L50S. MAIN UPR LEVEL LOW PROGGED TO SLOWLY EJECT EAST FROM NATIONS MID SECTION MONDAY TO THE OHIO/TNN VLLY WED. MODELS CONTINUE TO SHOW A SCNDARY LOW DVLPNG OVR THE MID ATLNTC REGION THURS WITH A TRAILING COLD FRONT PUSHING DEEPEST MOISTURE OFFSHORE LATE THURSDAY FOLLOWED BY LAGGING UPR LVL MOISTURE ACROSS THE AREA. NUMEROUS FORECAST CHALLENGES DURING THIS PRD. PRIME OF WHICH WILL BE THE LOCATION OF FRONTAL BOUNDARY NOW PROGGED TO HOVER SOMEWHERE ARND THE NC/VA BORDER TUES THRU THURS. THE UNCERTAINTY HERE WILL MAKE A PROBLEMATIC FORECAST FOR TMPS...WIND DIRECTION AND PCPN TYPE (I.E. CONVECTIVE VS STRATIFORMED). BETTER CONFIDENCE TODAY THAT THE TUES THRU WED TIME FRAME WILL BE THE WETTEST...SO HAVE INCREASED TO LIKELY POPS THEN. OTW...KEPT PCPN SHOWERS CWA WIDE FOR NOW GIVEN THE LOW CONFIDENCE THIS FAR OUT. COULD VRY WELL END UP BEING MORE OF A STRATIFORMED RAINFALL ACROSS THE PIEDMONT IF A COOL E-NE WEDGE SETS UP AS WELL AS HAVING TO ADD THUNDER TO THE SOUTHERN ZONES GIVEN A FRONTAL BOUNDARY LOCATION FARTHER NORTH. ALL-IN-ALL...EXPECT A COOL AND WET PRD. HIGHS GNRLLY FROM THE L-M60S NORTHERN HALF OF FA TO U60S-L70S SOUTHERN HALF. LOWS U40S- M50S. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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VFR CONDITIONS ARE EXPECTED THROUGH FRIDAY MORNING. SURFACE HIGH PRESSURE RIDGE WILL MOVE OFF THE COAST OVERNIGHT. A COLD FRONT APPROACHES FROM THE WEST FRIDAY MORNING AND CROSSES THE REGION LATE IN THE DAY. A BAND OF SHOWERS AND A FEW THUNDERSTORMS IS EXPECTED TO SET UP AHEAD OF THE FRONT. CONFIDENCE FOR SHOWERS AND MVFR CONDITIONS IS HIGH ENOUGH TO INCLUDE IN THE RIC AND SBY TAFS FRIDAY AFTN. TSTM ACTIVITY CAN BE ADDED IN LATER ISSUANCES WHEN TIMING OF ANY TSTMS BECOMES CLEAR. ANY IFR IS EXPECTED TO BE BRIEF. SOUTHEAST TO SOUTH WIND GUSTS TO OVER 20 KNOTS (AROUND 25 KNOTS AT ORF ECG AND PHF) ARE FORECAST FRIDAY AFTERNOON. OUTLOOK...PCPN MOVES ENDS SHORTLY AFTER THIS TAF PERIOD FRIDAY EVENING. DRY WEATHER AND MAINLY VFR IS INDICATED FRIDAY NIGHT THROUGH MONDAY. A SLOW MOVING LOW PRESSURE SYSTEM WILL SPREAD UNSETTLED WEATHER WITH PERIODS OF RAIN NEXT WEEK BEGINNING TUESDAY.
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&& .MARINE... NO HEADLINES TONIGHT AND FRI MORNING AS HIGH PRS BUILDS OVER THE WATERS. EXPECT VARIABLE WINDS TO BECOME S-SE BY MORNING. PRS GRDNT INCREASES AHEAD OF APPRCHG COLD FRONT FRI. DATA SHOWING HIGHER CONFIDENCE FOR AT LEAST MINIMAL SCA`S ACROSS THE CHES BAY FRI AFTRN. FROPA FRI EVENING WITH A WIND SHIFT TO W-NW AFTR MIDNIGHT. ALTHOUGH DATA SHOWS LITTLE IN THE WAY OF CAA...EXPECT A FEW HR PRD OF MINIMAL SCA RIGHT BEHIND FROPA SO WILL KEEP SCA`S THROUGH THE NIGHT ACROSS THE CHES BAY. OTW...EXPECT WINDS & SEAS TO STAY BLO SCA LVLS ACROSS CSTL WTRS ATTM. WEST WINDS ERLY SAT AHEAD OF A WEAK TROF PROGGED TO CROSS THE WATERS SAT AFTRN. WIND SHIFT TO THE N BEHIND THIS FEATURE...BUT KEPT WINDS BLO SCA LEVELS AS MOST MODELS PROGG WEAK ADVECTION BEHIND THIS FTR. GFS SOMEWHAT STRONGER WITH ITS SURGE AND HAS WINDS INTO MINIMAL SCA LEVELS SAT NITE. WILL TAKE A CLOSER LOOK AT THIS TOMORROW. LARGE UPR LVL SYSTM XPCTD TO APPRCH THE AREA NEXT WEEK. ALTHOUGH WINDS NOT THAT STRNG...WNA SHOWING INCRG SWELL WITH SEAS 5-7 FT BY THE MIDDLE OF NEXT WEEK. HAVE SPLIT THE DIFFERENCE BUT INCRSD SEAS TO 4-6 FT FOR NOW. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM FRIDAY TO 4 AM EDT SATURDAY FOR ANZ630>632-634. && $$ SYNOPSIS...AJZ NEAR TERM...AJZ/JDM SHORT TERM...AJZ LONG TERM...MPR AVIATION...LSA MARINE...MPR

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